Earlier on Twitter I circulated an interesting recent paper a commenter pointed me to- Hypogonadism and erectile dysfunction associated with soy product consumption. The paper documents the case of a 19 year old who had type 1 diabetes, but no other health problems. After starting a vegan diet he experienced alarming erectile dysfunction and general loss of libido. Upon examination, low testosterone levels were found.

Occasionally people will assert that evolutionary nutrition should involve mostly plants. After all, they read somewhere that the !Kung eat most of their calories from plants. And their nutrition science professor said so. Or some vegan book they read. And it's politically correct, so why not?